In the field of ultrasonic diagnostics, acoustic images of anatomical structures are utilized in the diagnosis of various medical disorders. In order to produce real-time images of the anatomic structures, beams of ultrasonic energy from a probe are transmitted into the body tissue of a patient and echoes received by the ultrasonic probe are rapidly processed into an image format suitable for display. It is desirable that the probe produce an image over a wide field of view using a sector scan format. A sector scan format generates an image by repeatedly transmitting and receiving ultrasonic energy in radial directions away from the probe to define a fan-like pattern. The ultrasonic beam is directed by mechanically moving an ultrasonic transducer such that it is swept through an arc about a pivot axis to produce the fan-like sector scan pattern.
The prior art is replete with examples of ultrasonic transducer probe assemblies, such as those disclosed in U.S. Pat. No. 4,149,419 entitled "Ultrasonic Transducer Probe" issued Apr. 17, 1979 to R. Connell et al.; U.S. Pat No. 3,955,561 entitled "Cardioscan Probe" issued May 17, 1976 to R. Eggleton; U.S. Pat. No. 4,421,118 entitled "Ultrasonic Transducer" issued Dec. 20, 1983 to J. Dow et al.; U.S. Pat No. 4,479,388 entitled "Ultrasonic Transducer and Drive System" issued on Oct. 30, 1984 to T. Matzuk; U.S. Pat. No. 4,399,703 entitled "Ultrasonic Transducer and Integral Drive Circuit Therefor" issued on Aug. 23, 1983 to T. Matzuk; U.S. Pat No. 4,092,867 entitled "Ultrasonic Scanning Apparatus" issued on Jun. 6, 1978 to T. Matzuk; U.S. Pat. No. 4,246,792 entitled "Self-Contained Ultrasonic Scanner" issued Jan. 27, 1981 to T. Matzuk; U.S. Pat. No. 4,398,425 entitled "Ultrasonic Scanning Transducer" issued on Aug. 16, 1983 to T. Matzuk; U.S. Pat No. 4,841,979 entitled "Ultrasonic Prostate Probe Assembly" issued on Jun. 27, 1989 to Dow et al.; and U.S. Pat. No. 4,913,155 entitled "Ultrasonic Transducer Probe Assembly" issued on Apr. 3, 1990 to Dow et al.
Although all of the above-referenced patent disclosures address various problems associated with the use of ultrasonic transducer imaging, none have addressed the particular problems associated with the use of an ultrasonic transducer probe for the imaging of elongate anatomical structures such as blood vessels in the peripheral vascular system. Furthermore, none of the cited patent disclosures address the problem of measuring fluid flow through such an elongate anatomical structure while simultaneously providing real-time imaging of the structure.
It would be desirable to provide real-time imaging of elongate portions of the peripheral vascular system and simultaneous measurements of the flow of blood therethrough. More particularly, it would be beneficial to provide real-time imaging of the carotid artery while simultaneously measuring the flow of blood therethrough in order to determine the presence of any pathologies, abnormal structures or conditions, and/or any indication of problems elsewhere within the vascular system, i.e., as provided by the blood flow rate.
Prior art ultrasonic probe assemblies have been ineffective in providing a satisfactory means for real-time imaging of elongate anatomical structures such as portions of the peripheral vascular system due to the sharp radius of curvature followed by the ultrasonic transducers thereof and additionally due to their inability to provide simultaneous blood flow measurements. The use of such a sharp radius of curvature is inherent in prior art devices due to the mounting of the ultrasonic transducer in immediate proximity to the pivot axis thereof. That is, the radius of the arc traveled by the ultrasonic transducer in such prior art devices is typically approximately 5-10 centimeters in length. Thus, the path traveled by the ultrasonic transducer is sharply curved and consequently suitable only for the imaging of comparatively small areas.
As such, although the prior art has recognized to a limited extent the problem ultrasonically imaging portions of the human anatomy, the proposed solutions have to date been ineffective in providing a satisfactory remedy.